Update for posterity: The new OE spacer/donut disintigrated on install, and reclogged the passageway. Even though I oiled it before installing, and was super careful, as soon as I installed the nozzle, air would not flow through it... and the last few turns of the nozzle were tighter than I've noticed previously.Once I pulled the nozzle back out, I could seen shreds of rubber in the threads, and after several attempts and cleaning it up and reseating it, it was destroyed on removal, and I had to unclog both the brass fitting and the nozzle.

Pretty ridiculous. The only thing I can determine is that these are super delicate and prone to falling apart, and it takes very little to clog it all up. Basically, if you use a mityvac on a good nozzle, you should be able to push air into the chamber without building up any pressure... if you see pressure on the gauge, or hear the "pop" when you pull off the line, it's not flowing. Same for vaccum with a broken nozzle (check valve)... if it builds up vacuum, you've got more wrong than the check valve itself.

I'm going to just try the new nozzles with the rear housing having no donut in it. I can't imagine it makes a huge difference, since I don't believe the housings these cars came with originally had them.

Just to clarify 100% as there are multiple parts involved here.

Are you using:
New style injector w/smaller hole
Rubber o-ring spacer
old style brass jet with slot

I don't think the brass jet with the slot is "old"... my housings were new, and I also just bought two brass jets with slots from Atkins.

Current injectors with be new style (small hole) with custom upgrade check valves in them, and a rubber spacer in the front housing, not in the rear.

Interesting, when did you purchase the housings? I assumed all new housings came with the non slotted brass jet. I see no reason to run any rubber grommet between the injector and brass jet with a slot, nothing would seal?

I can't remember exactly on the housings, but Atkins sent me two slotted inserts (you can find therm pictured on their site), last fall.

P

Some time ago I had asked Banzai Racing about the orifices. The slotted one is the old style that may be why the rubber insert got destroyed.

Well, well, well.

Interestingly, what I got from Atkins just last fall is definitely the taller slotted jet... but I also note they don't sell the rubber donut when I went to buy those. I think they must have a bunch of NOS slotted jets.... When I did my motor, it needed one replacement (used) housing, and it must've had the old style in there... which is taller, so if you add the donut, its almost certainly going to distort and block the flow.

Now mind you, I've blown both nozzles before, but well see how this new set up works before I go digging the donut out of the front housing to see what's in there.

So the diagram on page two is correct.? Grey color represents a cavity and the old design shows the slot present and the new design does not. This makes more sense to me and could explain why air would not flow through the nozzle when you installed the new donut(got crushed).

It's horribly obnoxious that there is no effective way to remove the oil jet from the housing. And it would be nice if the donut was simply another brass insert instead of rubber...

It seems the brass insert is just a solid piece of brass with holes drilled in it - no check valve or anything weird. The good thing is it really shouldn't need to come out or be replaced, just cleaned out.

Peter, with the problems you've had with the Mikuni, at this point does it seem like the problems could stem from the brass inserts being different sizes and whatnot?

Dale

I honestly don't think it has anything to do with the Mikuni, I ran it for years with no problem with both a TT and single T car. I think it was the fact that the used housing in my new motor had an oring installed on the old-style (taller) brass jet (which wouldn't be apparent to the naked eye), which prevented it from working, AND I think the quality of the new check valve nozzles isn't great, and I wonder if over all the new design combo both performs better but is more prone to failure, since we are hearing more and more about this. Add in thicker 20/50 oil, track use, etc., just the perfect storm.

I got the flu this week, so haven't put the car back on the ground to test, but I will try to verify all this as soon as I can. The test proceedure I outlined is the best way to tell what's going on.

P